1. Field of the Invention
This invention relates to a method for treatment of rubber and plastic wastes and apparatus therefor, and in particular, to a method for liquefying the wastes by pyrolysis and apparatus therefor.
2. Description of the Prior Art
Two conventional liquefying processes are known for treatment of rubber and plastic wastes. One process comprises heating and melting the rubber and plastics, feeding the molten substances to a pyrolysis reaction furnace and decomposing and dry-distilling the molten substances at the same time in the reaction furnace to liquefy the decomposed products. The other process comprises feeding the plastics directly to a pyrolysis reaction furnace and heating and melting the plastics therein using a heat transfer duct or the like with a simultaneous decomposition and dry-distillation thereof employing the molten substances as a heat transfer medium thereby to liquefy the decomposed products. In these conventional processes, the temperature in the heating means is almost uniform as a whole including the decomposing means and the dry-distilling means. This is, however, somewhat defective for the following reasons. If the temperature is to be elevated in order to accelerate the decomposition speed, the temperature must be elevated in all of the pyrolyzing means. However, rubber and plastics themselves have poor thermal conductivity, and therefore it is difficult to elevate the temperature in the pyrolyzing means easily. Accordingly, a specific heater which can elevate the temperature in the pyrolysis means much higher than is required or a lot of heaters must be used therefor. Various trials have heretofore been effected in an effort to accelerate the decomposition speed and to improve the decomposition efficiency, but no effective means have as yet been found. Accordingly, generally in the conventional processes, the pyrolysis is carried out for a long period of time at a temperature of 400.degree. to 500.degree. C. In order to treat a large amount of wastes, pyrolysis of the wastes for a long period of time in an apparatus provided with a large-sized decomposing trough has been suggested.
Moreover, conventional processes are further defective in that the pyrolyzed products are not uniform, and oils having quite different properties are recovered and obtained. The properties of the recovered oils vary widely in the treatment of any rubber and plastic materials, and the recovered oils comprise various kinds of components of an extensively broad range of from a light fraction having a fairly low flash point to waxes having a high pour point.